Good question and I think the answer is very few of us.
All the more reason to make sure you have 1 year of food stored up. And anything else you cannot live without.
That garden may not take off the first year.
thing is - If you don't already have your gardens established - and fruit tress/berries/well/laying hens etc - established - and haven't learned the 'old' skills like: make butter, soap, can, hunt (dress game) know and forage local wild plants, fish, etc - you're gonna have a less than even chance of survival.